Smart Traffic Light

IEC 61131-3 Structured Text traffic light controller — a demo project for STruC++.

Overview

This project implements a smart traffic light intersection controller using IEC 61131-3 Structured Text. It demonstrates how to structure, compile, and test an ST project using the STruC++ compiler in a CI pipeline.

Features

• Enum types with CODESYS dot notation (TrafficState.RED)
• Function blocks with methods, EXTENDS, and OVERRIDE
• State machines using CASE statements with enum labels
• Timer-based phase control using TON standard function block
• Dynamic memory with POINTER TO, __NEW, __DELETE
• Variable-length arrays (ARRAY[*] OF TIME)
• Located variables for physical I/O mapping
• CONFIGURATION/RESOURCE/TASK project structure
• Automated testing with STruC++ test framework

Getting Started

Install STruC++:

# Via npm
npm install -g strucpp

# Or download from releases
# https://github.com/Autonomy-Logic/STruCpp/releases

Compile the project:

strucpp \
  src/DataTypes/TrafficTypes.st \
  src/Functions/TimingUtils.st \
  src/FunctionBlocks/TrafficLight.st \
  src/FunctionBlocks/PedestrianLight.st \
  src/FunctionBlocks/VehicleDetector.st \
  src/FunctionBlocks/TrafficLogger.st \
  src/Programs/IntersectionController.st \
  -o build/intersection.cpp

Run tests:

strucpp --test src/DataTypes/TrafficTypes.st src/FunctionBlocks/TrafficLight.st tests/test_traffic_light.st

Project Structure

src/
├── DataTypes/        # ENUM and STRUCT type definitions
│   └── TrafficTypes.st
├── Functions/        # Standalone functions (timing utilities)
│   └── TimingUtils.st
├── FunctionBlocks/   # Function blocks
│   ├── TrafficLight.st       # Base traffic signal state machine
│   ├── PedestrianLight.st    # Pedestrian signal (EXTENDS TrafficLight)
│   ├── VehicleDetector.st    # Sensor-based vehicle counting
│   └── TrafficLogger.st      # Circular buffer event logger
└── Programs/         # Main programs
    └── IntersectionController.st  # 4-way intersection coordinator
tests/                # Test files using STruC++ test framework

CI

This project uses GitHub Actions with setup-strucpp to compile and test on every push and pull request.

License

MIT